1. Field of the Invention
The present invention relates to a packing element for an exchange column, either mass transfer or heat exchange, and more particularly to such multiple-member packing elements consisting of a plurality of adjacent, parallel, corrugated plates, with the corrugations of adjacent plates abutting one another forming fluid-receiving channels therethrough.
2. Description of the Prior Art
Many commercial chemical processes rely on the mass and heat transfer advantages provided by packed columns. such processes can include distillation, absorption and desorption, gas cleaning and drying, and various biological processes, particularly forms of filtration. In the majority of cases, two fluids, normally a gas and a liquid, are intermingled within a column, typically as counter-current flow streams. The reaction rates for these chemical processes are directly proportional to the amount of effective surface area within the column or tower over which the two fluids can reactively interface with one another. Packing elements are placed in the towers to increase the amount of surface area available for such interfacing, and one type of packing element that has been used consists of a multi-layered construction of parallel, corrugated plates.
The plates are generally made of sheet metal and are placed in contact with one another such that the folds or corrugations are at an angle to the column or tower axis. The plates themselves are disposed in planes that are parallel to the tower axis, thus maximizing the flow rates of the two fluids through the corrugated plates. When placed in such an attitude, and because the individual plates are formed out of sheet metal, problems have been experienced in obtaining a uniform distribution of the liquid over the surface of the plate. This can be a severe disadvantage since uniform distribution is essential for an effective mass transfer or heat exchange process when utilizing a gas as one of the fluids.
A further disadvantage with the corrugated-plate packing elements has been the tendency of the liquid fluid to flow down the folds or corrugations instead of evenly coating the plate surface while flowing from fold to fold. This "channeling" significantly decreases the reactive surface area available to the other fluid, and simultaneously increases the rate of flow-through of the liquid. These two events have almost a synergistic effect with one another, magnifying the decrease in the amount of reactant products and product yield for the packed tower.
The structure taught by Bredberg, U.S. Pat. No. 3,262,682, respnds to these problems by providing liquid-absorbing, corrugated sheets in the packing element. The sheets are, to some extent, self-wetting upon the application of the liquid-phase material, In addition. the liquid-absorbing sheet also tends to reduce the run-off problems. Both of these same disadvantages of corrugated plate elements are also addressed in Meir, U.S. Pat. No. 4,296,050, by providing fine grooves and random apertures in the folded surfaces. The capillary action generated by the fine grooves (termed "fluting" in Meier), assists in the wetting of the element surfaces. The random holes also provide such a wetting effect by forcing the liquid to move in a lateral direction, around the hole, in effect acting like an obstruction to the liquid stream.